The detail you and a lot of other respondents seem to be missing is that they actually did do research (at least it sounds like they ran some focus groups), and

The detail you and a lot of other respondents seem to be missing is that they actually did do research (at least it sounds like they ran some focus groups), and one of the things they discovered is that pregnant women were feeling the most ill and in need of a seat the most were early in their pregnancy and not showing yet. I'm sure many would feel uncomfortable asking someone to move for them, so having an established non-confrontational mechanism could help. On the other hand, I would echo many of the sentiments in this thread - I make it a point to stand unless there are many empty seats, but I've also been spontaneously engaged for an argument by a women who was insulted that I stood after she boarded the train. So I often just stand the whole time to avoid it all.